Calculating dependencies... done!
>>> Calculating removal order...
>>> These are the packages that would be unmerged:

!!! 'app-editors/nano' (virtual/editor) is part of your system profile.
!!! Unmerging it may be damaging to your system.

app-editors/nano
selected: 2.2.5
protected: none
omitted: none

All selected packages: app-editors/nano-2.2.5

>>> 'Selected' packages are slated for removal.
>>> 'Protected' and 'omitted' packages will not be removed.

this happened on my desktop installation. an upgrade on notebook having system almost similar to desktop (same profile, a subset of desktop packages, whatever) behaves normally. just observed that message in the forum seems to have the close problem source: virtual/editors ebuild contains "logical or" dependences: RDEPEND="|| ( app-editors/nano ....

what to do then? any ideas? (for sure i do know `emerge --noreplace' option :))

do you have another editor installed?
I think I ran into the same issue, but wasn't worried as I have vim installed, I prefer it over nano._________________read the portage output!
If my answer is too concise, ask for an explanation.

on both desktop and notebook i do have emacs installation. i also do not worry about the case of nano existence in my system..

however the question was why these two similar systems behave differently. actually this is my guess about similarity, at least i'm continuously trying to have these similar - for equal environment at home and out of home work

Could you compare your world files?
I might be that, nano is included in your notebook config, and not in your desktop's._________________read the portage output!
If my answer is too concise, ask for an explanation.